Means for driving large clock hands



MEANS FOR DRIVING LARGE CLOCK HANDS Filed May 22, 1934 4 U6 3 6 WWW i m m n .5 e H H Patented Mar. 17, 1936 UNITED STATES PATENT OFFICE 2,034,498 MEANS FOR DRIVING LARGE CLOCK HANDS Henry E. Warren, Ashland, Mass, assignor to Warren Telechron corporation of Maine Company, Ashland, Mass, at

Application May 22, 1934, Serial No. 726,881

6 Claims.

sume, for example, a clock having a. minute hand one hundred feet in length and otherwise proportioned to resemble an ordinary clock from a distance. It is impracticable and probably impossible to cover the dial of such a clock with glass. Such a clock hand willvhave a large surface area which, in use at exposed elevations, will be subjected to wind The wind load on a clock hand, such as referred to above, may easily reach several tons. It is the object of my invention to provide a method and apparatus for driving and properly supporting clock hands of th general character above referred to.

In carrying my invention into effect, I provide supporting means at the tips of the pointers. This may take the form of suitable rollers on the pointers running on circular guide tracks about the dial. I prefer to drive the pointers with individual synchronous electric motors mounted on the pointers near the tips and geared to circular racks concentric with the dial. For setting the, clock hands, these motors may be individually controlled.

The features of my invention which are believed to be novel and patentable will be pointed out in the claims appended hereto. For a better understanding of my invention reference is made in the following description'to the accompanying drawing in which Fig. 1 shows a face view and Fig. 2 a side view of portions of a large clock hand illustrating the general manner in which a clock hand of the size under consideration may be constructed; Fig. 3 illustrates how the tip ends 01 hour and minute hands of a large clock may be supported and driven; Fig. 4 indicates how electrical energy may be conveyed to the electrical driving motors located on the clock'hands; and Fig. 5 illustrates a face view of such a clock as viewed from a distance.

Referring now to Figs. 1 and 2, it will be noted that the supporting structure of the clock. hand;

illustrated is of a truss construction. This framework may be made from steel girders I at the four corners running lengthwise of the pointer and connected at numerous points by steel crosspieces II and diagonal braces l2. The joints may be provided with suitable angle plates l3 and the parts welded or riveted together as is common in truss steel constructions of this acter.

forming an observation plate [4 having an outline in the shape of a clock hand. All parts will be painted and the structure will otherwise be tadapted for exposure to outdoor weather condiions.

A one hundred foot represented in Figs. 1 and 2 and located outdoors sures likely to be encountered. It is calculated that the wind load normal to the face of such a pointer may reach 34,000 pounds and the wind load normal to the edge may reach 6,200 pounds, and the design is made to withstand these stresses without damage or displacement.

, 2O gThe pivot end is supported on a suitable hub I having a bearing on a stationary shaft l6. In securing the pointer structure to the hub, swivel joints are used at the two sides of the pointer as represented at I1 and I8 pivoting the pointer to ,the hub on an axis at right angles to the shaft and pointer. This permits a limited amount of bending or flexing of the pointer structure ina direction normal to its face without placing an undue strain on the bearing tending to bend the shaft I6.

The tip end of the pointer is provided with two rollers and 2| which run between track rails 22 and 23 with a slight clearance. The stationary track is circular and extends around the inner edge of the rim of the clock dlal concentric therewith. The rollers preferably have roller bearings running on stationary shafts 24 extending radially from the tip end of the pointer and displaced circumferentially from each other in the plain of rotation of the pointer two extreme edges of the pointer at this point. The roller shafts 24 are secured in a skeleton plate 25 extending across the tip end of the pointer structure and fastened four corner girders l0 and having braces 26 between the outer corners of the plate and the pointer structure back from the tip end. v

This manner of supporting the outer end of the pointer prevents any material movement of the pointer normal to its face at this point and, moreover, resists tipping stresses, does not prevent the pointer fro moving iii a circular path about the dial, but simply guiding it in such path.

beyond the between the ends of the tance than the diameter of the rollers For a one hundred foot pointer, the rollers and 2| may be separated by twelve feet, be 6 inches in outside diameter, and run between track rails separated by a slightly greater disso that one roller will not touch both rails at once. A

single rail track with rollers on either side may also be used.

The arrangement for driving the pointers in their circular paths is best shown in Fig. 3which represents a section through the edge of the clock dial 2'! together with portions of the ends of the minute and hour hands 28 and 29 lying adjacent thereto. The minute hand 28 is provided with a synchronous motor 30 and the hour hand 29 with a synchronous motor 3| supported on the truss construction beneath the observation plate l4; These motors drive suitable worm I gear speed reduction units which have their lorwspeed pinions represented at 32 and 33 in mesh with racks 34 and 35 fastened to the face" of the clock. The racks are circular concentric with the dial and have a radius corresponding to the radius of the pointers opposite these points. The

teeth in pinion and rack are cut sufliciently deep. so that the slight displacement of the pointers in a direction normal to the clock face to be 'ex-, pected at these points will not interfere with the driving engagement.

The tendency for the pinions 32 and 33 to move out of driving engagement with their racks 34 and 35 will not be serious as these driving engagements are made close to the tip ends of the pointers which are supported and any material displacement towards or from the clock face by the track and roller arrangement above described.

, t-ral slip ring 31 in common, that the return c ir- .60

It will be assumed that the synchronous motors are supplied with 60 cycle alternating current;

One manner of supplying such current is represented in Fig. 4 where l5 and I5 represent in outline the hubs for the minute and hour hand pointers. These hubs have hearings on the stationary shaft endwise displacement thereon. The hubs. are

provided with sleeves 38 and 3% which carry electrically insulated slip rings 31 and 31'. Stationary brushes 38', connected as shown to a source of supply 39 contact rings 31'. A pair of brushes 38 supported on hub I5 and electrically connected to twoof the slip rings 31' on this hub, contact with slip rings 31 on hub l5.

Supply circuits run from the slip rings on the hubs l5 and l5'to the synchronous motors 3i and 30 near the outer ends of the hour and minute-hands 29 and 28. It will be noted that both motors are supplied through wire 40 and the cencuit for motor 3i is through wire 4! and switch 42, and the return circuit for motor 30 is through wire --43 and switch 44. The motors may, therefore, be individually controlled and, consequent-' ly, the hour and minute hands may be individually set. After the pointers have been properly set, both switches 42 and 44 will remain closed. The same circuits may supply such lamps as it may be desirable to use on the pointers for illumination and such lamps are represented at 45. Circuit 46 is a circuit for supplying illuminating lamps 41 about the stationary part of the clock dial and this circuit will usually be opened at a switch 48 during daylight hours.

.The motor 30 for a one hundred foot minute hand having a total weight of about six thousand somewhat smaller and of less weight and moves- 1 at one-twelfth the speed of the minute hand, may

against tipping of the pointers.

i6 and are suitably secured against with the three slip 32 of 600 tol. The pinion 32 may then have 5 ten teeth and the rack 34 eighteen hundred teeth. This will cause the minute hand to be driven at the proper speed of one revolution per hour.

The motor 3| for the hour hand, which is be correspondingly smaller and its gear reduction will be higher.

The supporting flanges of racks 34 and 35 may be sunk to the level of the addacentclock dial surfaces and the guide rails 22 and 23 will preferably be flush with the adjacent surfaces of the clock dial so that, from a distance, these parts will not mar the appearance of the clock dial and may be so incorporated in the dial design as 20 to harmonize therewith, as indicated in Fig. 5.- The raised surface of the clock dial, indicated at 50 in Fig. 3, will appear asa band from a distant point and may have the time figures painted or otherwise mounted thereon as represented in 25 Fig. 5.

Indirect illumination, as represented in Fig. 3 may be provided and the minute hand may carry a few lamps on its under structure for furnishing illumination beneath this hand and .to make adjacent clock indications clearly visible and annul undesirable shadowing of the hour hand when adjacent the minute hand. The braces 26 and plate 25 at the tips of the pointers while visible may be toned down by properv coloring and rendered practically unnoticeable. The truss construction-of the pointers and the motors with their gear reduction units will be hidden from view by the covering surfaces I have not attempted to illustrate details of the supporting structure of the clock dial asthis forms no part of the present invention and willvary with the nature of the supporting strucsture on which the clock is mounted. It is sufiicient to state that the racks and guide tracks I must be firmly securedand braced in place by whatever construction is employed.

, In the foregoing description, certain data applicable to a one hundred foot pointer has been given by way of example but not with any intention of confining my invention to a pointer or to a clock conforming to the data mentioned.

'In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new Letters Patent of the United States is:

l; A clock comprising a dial, minute and hour hands pivoted at the center of said dial, a synchronous motor carried by each of said hands, a a

pair of circular racks concentric with said dial,

and speed-reducing gear trains carried by said hands connecting said synchronous motors in driving relation with said racks.

2. A clock comprising hour and minute hands,

a dial, a-shaft rotatively supporting said hands at the center of the dial, circular racks supported on the face of the dial concentric therewith, synchronous motors supported on the hands in 75 as v desire to secure by a synchronous electric motor carried by said structure for driving the same, the sheet metal covering concealing said motor and truss construction when the pointer is viewed from the covering side thereof.

4. A clock including a dial, a clock hand, a shaft at the center of the dial for rotatively supporting said hand, means for supporting the outer end of said hand against displacement in a direction normal to the face of the dial while permitting its rotation about the dial, a hub for said hand mounted on said shaft, and means for pivoting said hand to said hub on an axis at right anglesto said shaft and hand to relieve said shaft from bending stresses due to any bending of said hand. Y

5. A clock having a dial, a clock hand rotatively supported at the center of said dial and means for supporting the outer end of said hand against tipping and movements normal to the face of the dial while permitting its rotation comprising a pair of rollers rotatively mounted on radial axes at the outer end of the hand and spaced apart in the plane of rotation of the hand, and a circular track concentric with the dial having rails spaced apart a distance slightly greater than the outer diameters of said rollers in a direction normal to the clock dial and between which rails said rollers extend.

6. A clock comprising a dial, hour and minute hands pivoted at the center of said dial, the hour hand being shorter than the minute hand and located between the latter and the face of the dial, said dial having a portion adjacent to which the hour. hand rotates and a raised concentric portion adjacent which the outer end of the minute hand rotates, said portions lying parallel to said hands, rollers secured to the outer ends of said hands, circular tracks concentric with said dial in engaging relation with said rollers for supporting said hands while allowing their rotation about the dial, synchronous motors and speed-reducing gear trains driven from the motors on each hand near their outer ends, and

circular racks in the depressed and raised portions of said dials and concentric therewith with which the gear trains engage in driving relation.

HENRY E, WARREN. 

